radhaw
It's my understanding that copyright automatically applies once you've created something, but you might want to put a copyright notice somewhere in your game.
[quote:1uba0dsy]© 2017, My Company Name, All rights reserved.
If you want to do something "official" there are various organisations where you can register copyright, just look for the one in your country, but it's not strictly necessary.
Google is your friend if you need more information, but honestly unless your game is super unique I would't worry about it too much.